AU2008229820A1

AU2008229820A1 - Modular stem inserter

Info

Publication number: AU2008229820A1
Application number: AU2008229820A
Authority: AU
Inventors: Stephen A. Alford; Rebecca M. Furbee; Megan A. Maness
Original assignee: DePuy Products Inc
Current assignee: DePuy Products Inc
Priority date: 2007-10-10
Filing date: 2008-10-08
Publication date: 2009-04-30
Also published as: EP2047826A1; CN101507664A; JP2009101152A; US20090099566A1

Description

AUSTRALIA Patents Act 1990 ORIGINAL COMPLETE SPECIFICATION INVENTION TITLE: MODULAR STEM INSERTER The following statement is a full description of this invention, including the best method of performing it known to us:- -2 MODULAR STEM INSERTER TECHNICAL FIELD OF THE INVENTION [00011 The present invention relates generally to the field of orthopaedics, and more particularly, to an instrument used to insert an implant for use in 5 arthroplasty. BACKGROUND OF THE INVENTION [00021 Patients who suffer from the pain and immobility caused by osteoarthritis and rheumatoid arthritis have an option of joint replacement surgery. Joint replacement surgery is quite common and enables many individuals to function 10 properly when it would not be otherwise possible to do so. Artificial joints are usually comprised of metal, ceramic and/or plastic components that are fixed to existing bone. 100031 Such joint replacement surgery is otherwise known as joint arthroplasty. Joint arthroplasty is a well-known surgical procedure by which a 15 diseased and/or damaged joint is replaced with a prosthetic joint. In a typical total joint arthroplasty, the ends or distal portions of the bones adjacent to the joint are resected or a portion of the distal part of the bone is removed and the artificial joint is secured thereto. 100041 There are known to exist many designs and methods for 20 manufacturing implantable articles, such as bone prostheses. Such bone prostheses include components of artificial joints such as elbows, hips, knees and shoulders. [00051 Numerous instruments are required in performing a hip arthroplasty. The surgeon must use various reamers and broaches for cutting and shaping the 03/10/08,va 17551 speci.2 -3 bone. Additionally, when implanting the stem into the long bone, the surgeon must use a stem inserter. [00061 In hip arthroplasty, there are currently many different approaches, or surgical techniques in implanting the bone prostheses. The posterior approach 5 accesses the joint through the back, gives straightforward access to the acetabulum, provides good visualization of the femoral shaft, and allows the surgeon to preserve the hip abductors. The anterolateral approach exploits the intermuscular plane between the tensor fasciae latae and the gluteus medius, involves partial or complete detachment of the abductor mechanism, and combines good exposure of the 10 acetabulum with safety during preparation of the femoral shaft. The anterior approach utilizes the internervous plane between the sartorius and the tensor fasciae latae, exposes the hip without detachment of muscle from the bone, and takes advantage of the fact that the hip is an anterior joint, closer to the skin anteriorly than posteriorly. 15 10007] Because femoral access is different with each of the aforementioned approaches, it is desirable to use different stem inserters for each approach. Depending on how the surgeon approaches the femur, or long bone, an inserter with different angular or curved configurations may be preferred so as to best reach the stem/implant without impinging the bone or surrounding soft tissue. Surgeons may 20 also choose different angled/curved/offset inserters depending on the anatomy of the individual patients and the selected implants. Some surgeons also prefer to use multiple stem inserters at the varying stages of stem insertion during a single surgery. Like other surgical instruments, these stem inserters are housed in instrument cases that must conform to weight and size requirements. Unfortunately, the stem 03/10/08,va 17551 speci,3 -4 inserters' handles are quite bulky and can greatly reduce the available case weight and free space for other required hip arthroplasty instrumentation. The transportation, set-up, and sterilization of multiple heavy stem inserters can also become a burden to the surgical staff. Therefore, there is a need for a reduction in 5 the size and weight of surgical instruments used in joint replacement surgeries. 100081 The present invention is directed to alleviate at least some of the problems with the prior art. SUMMARY OF THE INVENTION 100091 According to one embodiment of the present invention, a kit for use in 10 implanting a stem into a long bone is provided. The kit includes a universal handle including a locking mechanism and a plurality of shafts. Each of the plurality of shafts is adapted to couple with the universal handle such that the locking mechanism of the universal handle locks each of the plurality of shafts to the handle. 100101 According to another embodiment of the present invention, a kit for 15 use in implanting a stem in a long bone is provided. The kit includes a handle and a removable shaft. The removable shaft includes an end portion for extending into the aperture to lock the removable shaft to the handle. 100111 According to yet another embodiment of the present invention, a method for inserting a stem into a long bone is provided. The method includes 20 providing a handle and a plurality of shafts. Each of the plurality of shafts including a handle-attachment end and a stem-attachment end. One of the plurality of shafts is selected and the handle-attachment end of the selected shaft is inserted into the handle. The stem-attachment end of the shaft is inserted into the stem and the stem is seated into the long bone. 03/10/08,va 17551 speci,4 -5 [00121 Other technical advantages of the present invention will be readily apparent to one skilled in the art from the following figures, descriptions and claims. BRIEF DESCRIPTION OF THE DRAWINGS [00131 For a more complete understanding of the present invention and the 5 advantages thereof, reference is now made to the following description taken in connection with the accompanying drawings, in which: [00141 FIG. I is a plan view of a modular stem inserter according to one embodiment of the present invention; [00151 FIG. 2 is a top view of the modular stem inserter of FIG. 1; 10 [00161 FIG. 3 is a side view of the modular stem inserter of FIG. 1; [00171 FIG. 4 is an internal, assembled view of a locking mechanism of the handle of the stem inserter according to one embodiment of the present invention; [00181 FIG. 5 is an exploded view of the locking mechanism of the stem inserter handle of FIG. 4 and the stem inserter shaft of FIG. 1. 15 [00191 FIG. 6 is an internal, assembled view of the stem inserter handle of FIG. 4 and stem inserter shaft of FIG. 1 [00201 FIG. 7 is a plan view of a modular stem inserter kit according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION 20 [00211 Embodiments of the present invention and the advantages thereof are best understood by referring to the following descriptions and drawings, wherein like numerals are used for like and corresponding parts of the drawings. [00221 Referring now to FIGS. 1-3, a stem inserter 10 according to one embodiment of the present invention is shown. The stem inserter 10 includes a 03/10/08,va 17551 speci,$ -6 handle 12 and a shaft 14. In the embodiment illustrated in FIG. 1, the shaft 14 is a curved anterior shaft used during the anterior approach. However, it should be understood that any type of shaft may be used, and the curved anterior shaft is for illustrative purposes only. 5 [00231 As shown in FIG. 1, the handle 12 is separable from the shaft 14. The handle 12 includes a shaft-attachment end 16 and an opposing end 18. The shaft 14 includes a handle-attachment end 20 and a stem attachment end 22. The stem attachment end 22 is designed to fit on to the end of a stem (not shown) for insertion into the long bone. The stem attachment end 22 of the shaft 14 may vary depending 10 on the stem's insertion feature. The shaft-attachment end 16 of the handle 12 includes an aperture 24 designed to receive the handle-attachment end 20 of the shaft 14. In the illustrated embodiment, the aperture 24 includes a flat end 26 that corresponds to a flat end 28 on the handle-attachment end 20. The flat ends 26, 28 ensure proper alignment of the shaft 14 and the handle 12 while also minimizing 15 rotational toggle. The opposing end 18 of the handle 12 serves as an impaction surface for the surgeon during stem insertion. 100241 Turning now to FIG. 4, an internal, assembled view of the shaft attachment end 16 of the handle 12 is illustrated. The shaft-attachment end 16 of the handle 12 includes a locking mechanism for securing the handle 12 to the shaft 14. 20 As shown in FIG. 4, the locking mechanism includes a spring-loaded button 30. The spring-loaded button 30 includes a spring 32 to lock the shaft 14 to the handle 12. 100251 FIG. 5 illustrates an exploded view of the handle 12 and the shaft 14. As illustrated, the handle-attachment end 20 of the shaft 14 includes a shaft tip chamfer 34. The angle on the chamfer 34 allows the shaft 14 to be inserted into the 03/10/08,va 17551 speci.6 -7 aperture 24 of the handle 12 without depressing the button 30. The chamfer 34 presses against a corresponding edge 36 of the button 30, which causes the button 30 to compress the spring 32, thus allowing the shaft 14 to be inserted. 100261 The shaft 14 also includes a shaft-locking slot 38 and a shaft-locking 5 ramp 40. When the shaft 14 is inserted into the handle 12, the shaft-locking slot 38 and the shaft-locking ramp 40 engage with the internal button base 42 of the button 30 in order to lock the shaft 14 into the handle 12. Specifically, once the shaft 14 is inserted into the handle 12, the spring 32 decompresses causing the button 30 to apply force to the shaft-locking ramp 40. This motion forces the shaft 14 up and into 10 the handle 12 to minimize toggle and ensure a secure lock. Once the shaft 14 is inserted into the handle 12, the shaft-locking slot 38 receives pressure from the button 30 to lock the shaft 14 to the handle 12. The shaft-locking slot 38 also prevents the shaft 14 from being pulled out of the handle 12 without first depressing the button 30. 15 100271 A stop pin 44 is included on the handle 12 and engages a slot 46 on the button 30. The stop pin 44 prevents the button 30 from falling out of the handle 12. Also, the slot 46, along with the stop pin 44, limits the travel of the button 30 in order to ensure that the locking mechanism of the handle 12 always functions properly. 20 100281 Also as shown in FIG. 5, the shaft 14 includes a flat impaction surface 48. The flat impaction surface 48 allows the surgeon's impaction force to transfer from the handle 12 to the shaft 14. The flat-impaction surface 48 ensures that excessive load is not applied to the various features of the locking mechanism (e.g., the spring-loaded button 30, the shaft-locking slot 38, etc...). 03/10/08,va 17551 speci,7 -8 100291 Turning now to FIG. 6, the modular stem inserter 10 is shown with the handle 12 and the shaft 14 in an engaged position. As shown, the spring-loaded button 30 has engaged the shaft-locking slot 38 (FIG. 5) of the shaft 14. The spring 32 (FIG. 5) is in a compressed position pushing the button 30 out, causing the 5 internal button base 42 (FIG. 5) of the button 30 to contact shaft-locking ramp 40 (FIG. 5), locking the shaft 14 to the handle 12. As identified in FIG. 6, the handle 12 and the shaft 14 have each been etched with an alignment triangle 49. The alignment triangles 49 indicate alignment of the flat end 26 (FIG. 1) of the handle 12 and the flat end 28 (FIG. 1) of the shaft 14, thus acting as a visual for easy insertion. This 10 feature allows the user to insert the handle-attachment end 20 of the shaft 14 into the aperture 24 of the handle 12 in any rotational orientation and then simply rotate the shaft 14 until the two alignment triangles 49 are aligned. The shaft 14 then snaps into the handle 12. [00301 Although in the illustrated embodiment the alignment triangles 49 are 15 triangular, it should be understood that other shapes or indicators could be used. Also, other known marking methods instead of etching may also be used to create these features. In some embodiments, the etchings 49 may not be included and instead, the user may assemble the handle 12 and the shaft 14 by feel. [00311 Turning now to FIG. 7, a kit 50 according to one embodiment of the 20 present invention is shown. In this embodiment, the kit 50 includes a handle 52 and four shafts 54a, 54b, 54c, 54d. Each of the shafts 54a, 54b, 54c, 54d includes a handle-attachment end 56a, 56b, 56c, 56d that is configured the same as the handle attachment end 20 illustrated in FIGS. 1-6 above. In these embodiments, because each of the handle-attachment ends 56a, 56b, 56c, 56d is of the same design, each 03/10/08,va 17551 speci.8 -9 shaft can be locked into the handle depending on the type of surgery or the surgeon preference. The illustrated kit includes the standard straight shaft 54a, the curved anterior shaft 54b, the posterior shaft 54c, and the bullet tip shaft 54d. [00321 During surgery, the surgeon will select the appropriate shaft based 5 upon the surgical approach, the surgeon's personal preference, and patient anatomy, as well as the type of stem being implanted. The surgeon will attach the selected shaft 54 to the handle 52 by pushing the two together, making sure the two alignment arrows 49 (Fig. 6) of the handle 12 and the shaft 14 are aligned. After introducing the stem by hand into the femoral canal, the surgeon then aligns the stem attachment 10 end 22 (Figs. 1-6) of shaft 14 with the stem's driver platform and continues the insertion process until the stem is properly seated. In some embodiments, the stem attachment end 22 of the shaft 14 may be threaded to correspond to threads in the stem. In such a case, the surgeon could then thread the stem-attachment end 22 of the shaft 14 onto the stem and use the stem inserter 10 to introduce the stem into the 15 femoral canal. [00331 In one embodiment, the handle 12 and the shaft 14 will be manufactured of a metal material. This metal could be a stainless steel including, but not limited to, precipitation hardening stainless steels such as 17-4, 13-8Mo, XM-13, 455, XM-25, and 465 or martensitic stainless steels such as 410, 416, 420, 431, 20 440A, 440B, and 440C. The instruments could also be manufactured out of a cobalt based alloy such as wrought CoCrMo (F1537), a hardened condition of Co-Cr-W-Ni (F90), cold worked MP35N (ASTM F562), or another metal material suitable for a medical application. In other embodiments, the handle 12 may be made of re-usable stainless steel while the shaft 14 is a disposable device made of a plastic material. 03/10/08,va 17551 speci.9 -10 This plastic may or may not contain reinforcement and could be ABS, polypropylene, polyurethane, polyesters, Acetals, or Polyimide. This is a representative list and does not exclude other plastics or polymer systems that are used for medical applications. 5 100341 Although the above-shown embodiments depict four different types of shafts, any number of shafts may be included. The shafts may be shaped to relate to a particular surgical technique, a different type of stem, a surgeon's preference, or even a particular stage of the impaction process. The shafts may also have a threaded stem attachment end 22 in order to provide the surgeon greater version and 10 insertion control. [00351 Also, although the locking mechanism has been described as a spring loaded button cooperating with a shaft-locking slot, it should be understood that other types of known locking mechanisms may be utilized such as a ball plunger, interlocking teeth, Hudson end, prongs and/or circular springs. 15 [00361 In other embodiments, the shaft-tip chamfer may not be utilized, and the user may have to activate the locking mechanism by depressing the button 30 in order to insert the shaft into the handle. [0037] Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions, and 20 alterations can be made therein without departing from the spirit and scope of the present invention as defined by the appended claims. Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or 03/10/08,va 17551 special - 11 group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. The reference to any prior art in this specification is not, and should not be 5 taken as, an acknowledgment or any form or suggestion that the prior art forms part of the common general knowledge in Australia. 03/10/08.va 17551 speci, I I

Claims

1. A kit for use in implanting a stem into a long bone, the kit including: a universal handle including a locking mechanism; and 5 a plurality of shafts, wherein each of the plurality of shafts is adapted to couple with the universal handle such that the locking mechanism of the universal handle locks each of the plurality of shafts to the handle.

2. The kit of claim 1, wherein the locking mechanism includes a spring-loaded button. 10

3. The kit of claim 2, wherein the handle includes a stop pin adapted to engage a recess in the spring-loaded button.

4. The kit of claim 1, wherein each of the plurality of shafts includes an identical end portion to lock with the locking mechanism.

5. The kit of claim 1, wherein the plurality of shafts includes at least two of a 15 standard straight shaft, a bullet tip shaft, a curved anterior shaft and a posterior shaft.

6. The kit of claim 1, wherein the handle is made of a metal.

7. The kit of claim 1, wherein each of the plurality of shafts is made of one of a metal or a disposable plastic. 20

8. A kit for use in implanting a stem in a long bone, the kit including: a handle; a removable shaft, the removable shaft including an end portion for extending into the aperture to lock the removable shaft to the handle.

9. The kit of claim 8, wherein the handle is made of a metal selected from the group 25 of stainless steels. 03/10/08,va 17551 spcci,12 - 13

10. The kit of claim 8, wherein the handle includes a locking mechanism for locking the handle to the removable shaft.

11. The kit of claim 10, wherein the locking mechanism includes a spring-loaded button. 5

12. The kit of claim 11, wherein the removable shaft comprises shaft-tip chamfer for allowing the removable shaft to be inserted into the handle without activating the spring-loaded button.

13. The kit of claim 11, wherein the removable shaft includes a shaft-locking slot and a shaft-locking ramp for engaging the spring-loaded button of the handle. 10

14. The kit of claim 8, wherein the removable shaft includes a flat impaction surface to abut the handle, such that a force impacted on the handle transfers to the shaft .

15. A method for inserting a stem into a long bone comprising: providing a handle; providing a plurality of shafts, each of the plurality of shafts including a handle 15 attachment end and a stem-attachment end; selecting one of the plurality of shafts; inserting the handle-attachment end of the selected shaft to the handle; inserting the stem-attachment end of the shaft into the stem ; and seating the stem into the long bone. 20

16. The method of claim 15, further including locking the selected shaft to the handle.

17. The method of claim 16, wherein the locking includes activating a spring-loaded button on the handle. 03/10/08,va 17551 speci,13 - 14

18. The method of claim 17, wherein inserting the handle-attachment end of the shaft into the handle includes pressing a shaft-tip chamfer against the spring-loaded button.

19. The method of claim 17, wherein the spring-loaded button is held in the handle 5 by a stop pin.

20. The method of claim 15, wherein the plurality of shafts includes at least two shafts selected from the group comprising a standard straight shaft, a bullet tip shaft, a curved anterior shaft, and a posterior shaft.

21. The method of claim 15, wherein the stem-attachment end of the shaft is 10 threaded and inserting the stem-attachment end of the shaft into the stem includes threading the threaded stem-attachment end of the shaft into the stem. 03/10/08,va 17551 speci.14